Fibrosis is an intermediate result of and a pathological process itself leading from tissue injury through its encapsulation by extracellular matrix to a pathological formation of scar tissue.
Injury leading to fibrosis occurs in response to a variety of chronic insults including alcohol abuse, drugs, toxins, viral hepatitis B and C, some metabolic diseases, foreign objects, such as small mineral or organic particles (e.g., in the lungs), causing chronic and/or permanent tissue irritation, or other hepatic or pulmonary abnormalities. For example, an advanced stage of disordered connective tissue formation is cirrhosis, defined by the presence of encapsulated nodules, and eventually cancer.
Fibrosis is a systemic response to chronic injury, developing through a series of highly coordinated molecular events, collectively called fibrogenesis. In one example, fibrosis develops as a result of chronic mammalian liver injury. The steps immediately following chronic mammalian liver injury represent a process called “initiation”, which in turns are early events of “activation” of hepatic stellate cells. The next step of stellate cells activation is “perpetuation”, and this leads to proliferation, fibrogenesis and matrix degradation. Each of these events is accompanied by specific molecular markers, such as collagen I (a marker of fibrosis), alpha 1-smooth muscle actin (a marker on activation of stellate cells), beta PDGF-receptor (a marker of proliferation), matrix metalloproteinases and their inhibitors MMP2, MMP9, TIMP1 and TMP2 (markers of matrix degradation), cytokine TFG-β1 (a marker of fibrogenesis).
Development of fibrosis can be evaluated by the quantitative level of the respective markers. Reduction of fibrosis can be evaluated by the decrease of the level of the respective markers during various stages of fibrosis. Fibrosis can be reduced and reversed. Furthermore, even an advanced stage of fibrosis, cirrhosis, can be reversed.